Mouse Spiders

Family Actinopodidae, Missulena species

Identification

Male Whitebacked Mouse spider (Missulena bradleyi) showing all black head and pale bluish area on top of the body.Male Redheaded Mouse spider (Missulena occatoria), showing deep red head and dark royal blue abdomen.Burrow found in Brisbane.Burrow found in Western Australia, with two distinct doors.Female Mouse spider.

Stout black spiders. Body uniform black or dark blue, or black with a light grey to white patch on top. The head is very wide, shiny, and black, sometimes with bright red or orange-red chelicerae and eye region. Legs dark and may appear long and thin.

Females are larger, stockier, more solid spider with uniform black head and body. Males may vary from a 5 to a 20 cent coin in leg span.

Missulena is often confused with funnelweb spiders. When viewed from the side, the head of the mouse spiders appears as a step, strongly divided into two levels by a nearly vertical drop from the front half of the head. The eight tiny eyes are spread across the front of the upper section behind the very prominent chelicerae. In funnel-web and all other trapdoor spiders the eyes are grouped together on a mound at the centre front of the head and the head is not strongly divided.

When provoked, Missulena is aggressive and is quick to rise to the striking position. When viewed from underneath, the fangs of Missulena tend to cross at the tips whereas, in the funnel-web and all other trapdoor spiders, the fangs lie parallel when closed.

Males of the Redheaded Mouse spiders (Missulena occatoria) have a deep red head and chelicerae and a dark royal blue abdomen. Males of Whitebacked Mouse spiders (Missulena bradleyi) have an all black head and a pale bluish area on top of the body. Males of the third species, Missulena dipsaca, are all black and much smaller spiders than the other two species. Females of the three species have not been formally studied.

Diversity & distribution

Australia-wide but not Tasmania. These small to medium-sized trapdoor spiders are common in suburban gardens in Australia. The family Actinopodidae occurs also in South America.

Three species are recorded for Queensland:

Redheaded Mouse spiders (Missulena occatoria)

Whitebacked Mouse spiders (Missulena bradleyi)

Small Black Mouse Spider (Missulena dipsaca).

Burrow

Mouse spiders are quite common in many Queensland suburbs but not often seen. They make a very well concealed burrow in the lawn or open ground. Often the web tube flops onto the ground and is soil-encrusted and hence well-camouflaged.

Burrows may be located in lawns after rain by looking for small pyramids of soil beside which is a very well concealed tube.

The spiders are often found while gardens are being dug or soil turned over. Males wander from late Summer and tend to peak in April-May and often fall into suburban swimming pools whilst searching for females.

In Western Australia, mouse spiders make two distinct doors set up and side by side.

Bite

Mouse spiders are Probably our most enigmatic of biting spiders. Of all recorded and specimen-backed bites of the Mouse Spider (Missulena bradleyi) only one (to a 19 month old baby in Gatton) has caused serious reactions.

The seriousness of the bite of Missulena was until recently the subject of serious disagreement. We had recorded several reports of uneventful bites from Missulena species both males and females. Two reports stand out. In one, a 7-year-old boy had a female Mouse spider attached bull-terrier style to his finger. The GP had to crush the spider to get the fangs out. The boy complained only of minor hunger pains as in the excitement, lunch had been missed!

The second case was of a paramedic whose earth basement was almost swarming with male Missulena bradleyi. He was bitten repeatedly by the males in his sleeves. The immediate pain soon passed and he had no problems until 36 hours later when a large infected area appeared on his arm. He applied an antibiotic powder and the wound healed and was barely noticeable when we saw it a week or so later.

The late Dr Struan Sutherland’s research showed that these spiders were potentially more toxic than Funnelwebs; thus, we were at odds. Inexplicably, the Gatton baby recovered quickly when given Funnelweb antivenom. Clearly, the Gatton bite was what Sutherland had predicted but why did some victims not react?

Dr David Wilson, then at the Department of Drug, Design & Development, University of Queensland looked at the question. When Funnelwebs disturbed, they quickly rise to the defence pose with a drop of venom on each fang tip. However, although Missulena also rises to the defence pose quickly, venom is rarely seen.

It seems that the Mouse spider rarely needs or uses its much smaller reserve of venom; presumably most of the uneventful bites were dry, i.e., without venom.